胶东牟平-乳山成矿带金青顶金矿广域电磁法探测效果分析

Application Effects of the Wide Field Electromagnetic Method in the Jinqingding Gold Deposit in Muping-Rushan Metallogenic Belt,Jiaodong Peninsula

金青顶大型金矿床位于胶东东部牟平-乳山成矿带中段,是胶东地区硫化物石英脉型(金牛山式)金矿中的典型矿床。研究区内主要为断裂控矿,金矿体赋存于NNE向将军石断裂内,该控矿断裂发育在中生代玲珑花岗岩体内,倾向变化相对复杂,同时矿山开采带来了一定的电磁干扰,电磁法勘探难度较大。本次在金青顶金矿区开展广域电磁法(WFEM)探测试验,在围岩物性单一及工业电磁干扰等因素下,主要研究该方法对于较小规模复杂形态金矿控矿断裂的识别能力,并与传统的可控源音频大地电磁测量(CSAMT)探测效果进行对比分析。结果表明,在钻孔控制的-1100 m以浅范围内,WFEM法与CSAMT法均可达到较为理想的探测效果,前者对于将军石断裂倾向变化的地电异常响应更加细致,一定程度体现出广域电磁法的高精度探测特点;在-1100~-2500 m深度区间,广域电磁法推断解译的深部断裂线性串珠状低阻异常特征依然明显,且对深部断裂内低阻矿化体具有较强的局部识别能力,体现了该方法同时具有大深度探测优势。本次试验分析表明,广域电磁法能够有效弥补常规电磁勘探方法在本区的局限性,并同时满足区内高精度及大深度的金矿勘查需求,可较为清晰地反映出将军石控矿断裂的垂向形态特征,为金青顶矿区内今后开展深部金矿勘查及研究工作提供较为充分的地球物理依据,同时表明广域电磁法是适用于胶东地区硫化物石英脉型金矿探测的有效电磁勘探方法之一。

The large-scale Jinqingding gold deposit is located in the middle of Muping-Rushan metallogenic belt in Jiaodong Peninsula,which is a typical sulfide quartz vein type(Jinniushan type)gold deposit in the Jiaodong area.The ores show a significant control by faults,and gold orebodies mainly occur in the NNE-trending Jiangjunshi fault.This fault was developed in the Mesozoic Linglong granite body,and varied greatly in its strike.Also,previous mining brings certain industrial interference,which makes it difficult to explore by electromagnetic methods.This work conducted wide field electromagnetic(WFEM)detection to determine small-scale complex ore-control faults in case of single physical property of surrounding rocks and industrial electromagnetic interference in the Jinqingding gold deposit.The detection results were then compared with those of the traditional controlled source audio magnetotelluric method(CSAMT).The results show that both the WFEM and CSAMT methods can achieve ideal detection results at depth of>-1100 m penetrated by drill holes.The WEFM method displays more detailed geoelectric anomaly response to the strike change of the Jiangjunshi fault,indicative of its high-precision detection characteristics.At a depth range of-1100 m to-2500 m,the WFEM method can clearly identify linear beaded low-resistance anomalies of deep faults,and can well determine local deep low-resistance mineralized bodies,suggestive of its large-depth exploration advantages.The experimental analysis reveals that the WFEM method can effectively make up the shortage of conventional electromagnetic methods in this area,and can meet the demand of high-precision and large-depth exploration of gold mines.This method can pinpoint the vertical morphology of the ore-controlling Jiangjunshi fault,which provides a sufficient geophysical basis for the future exploration and research of deep gold Jinqingding deposit.It is inferred that the WFEM method is one of the effective electromagnetic methods for the exploration of sulfide quartz vein type gold deposits in the Jiaodong area.